The invention here is concerned with a backwater tank for a building connected to a vacuum drain facility, whose waste water is fed through gravity feed lines or conduits to a collector which is connected to a vacuum drainage conduit through a valve that opens automatically at a specific maximum water level. Moreover, the invention is particularly concerned with a waste water removal system such as disclosed in German Pat. No. 2,653,713, which corresponds to copending U.S. Application Ser. No. 855,086, filed on Nov. 28, 1977 now U.S. Pat. No. 4,120,312. In this patent, a connection is provided to a ventilated backwater tank. The volume of the tank is large in comparison to the gravity conduit or the said collector and the connection is provided at a level above the maximum water level in the collector.
Various embodiments of the backwater tank are described in the patent. However, in each instance, relatively complex, and hence expensive, installation operations are required, generally because the backwater tank, the check valve and the control device thereof have to be installed separately. Moreover, if the control device and the check valve were to be installed in a covered shaft separately from the backwater tank, there is the danger that in winter, this shaft could be so tightly compacted or sealed by ice and snow that a vacuum could be established from a lack of sealing of the valve of the vacuum-operated control device, so as to result in malfunctioning of the control device. It is also noted that prior art backwater tanks and control shafts for the check valve and the control device are characteristically located relatively deep in the ground and are relatively heavy, so that dredges or the like must be utilized for excavation work. In places where access is difficult, this leads to further complications.